Erwin Sietas (24 July 1910 – 20 July 1989) was a German swimmer who competed in the 1928 Summer Olympics, 1932 Summer Olympics and 1936 Summer Olympics.In the 1928 Olympics he was fourth in the 200 m breaststroke event.Four years later he was again fourth in the 200 m breaststroke event.In the 1936 Olympics he won a silver medal in the 200 m breaststroke event.
Won three medals in the men's 200 meter breaststroke in several European Championship games: A bronze medal in 1931, a gold medal in 1934, and a silver medal in 1938.